The data center at Lule is now handling live data traffic from around the world, with all the servers and other equipment powered by locally generated hydro-electric energy.

"Not only is it 100 percent renewable, but the supply is also so reliable that we have been able to reduce the number of backup generators required at the site by more than 70 percent," according to a Facebook statement.

In addition to harnessing the power of water, the Lule data center uses the chilly Nordic air to cool the thousands of servers. And any excess heat from those servers is harnessed and used to keep staff offices warm.

Open Compute Project design applied

All the servers used are also built using Facebook's Open Compute Project designs, which encourage the development of "vanity-free" hardware that leaves out "unnecessary bits of metal and plastic.

"These designs are then shared with the broader community, so anyone can use or improve them," Facebook said.

Facebook says the Lule data center is averaging an impressive power usage efficiency (PUE) rate "in the region of 1.07."